ALT Physical wave processors are constrained by diffraction, but the bandwidth of the mathematical functions they implement need not be set by it. Here, we demonstrate continuous and multiplexed optical processing of superoscillatory functions, in which a scalar argument is encoded onto a wavefront and a fixed diffractive wave processor synthesizes optical responses that approximate the corresponding function outputs in parallel. Unlike conventional superoscillatory optics that generates predetermined fields, superoscillation here is expressed in the input-output dependence on the encoded argument. Its frequencies are therefore distinct from the transverse spatial frequencies of propagating light and are not subject to the same diffraction-imposed cutoff. We demonstrate complex-valued superoscillatory function synthesis and introduce a multiplexed architecture that simultaneously evaluates distinct target superoscillatory functions whose harmonic content exceeds that of the optical input e

ALT Conventional thermal emitters obey Kirchhoff's law of thermal radiation, which ties absorptivity to emissivity and places a fundamental limit on a range of radiative energy technologies and sensing systems. This constraint can be overcome using magneto-optic materials, which exhibit nonreciprocal thermal emission under an applied magnetic field. While the spectral nonreciprocity of magneto-optic devices has been explored theoretically and experimentally, nonreciprocal control over the direction of thermal emission has received far less attention. Here, we propose and numerically demonstrate nonreciprocal beam steering of thermal emission, wherein an applied magnetic field lifts the degeneracy between guided modes at +/- kx, enabling asymmetric and tunable directional thermal emission. We highlight a III-V semiconductor photonic structure operating at 24.5 um, a wavelength with few laser sources. This structure exhibits a nonreciprocity greater than 0.5 between +/- 75 degrees at 50 mT,

ALT Multimode fibers (MMFs) offer a minimally invasive platform for deep-tissue and multisite in vivo optical sensing. Computational microendoscopy methods extend them into the high-resolution imaging domain, but are quite sensitive to experimental errors. This study investigates the robustness of microendoscopy based on compressive sensing (CS) by comparing step-index (SI) MMFs with graded-index (GRIN) fibers. Mode-expansion-based simulations are used to assess the accuracy of image reconstruction in the presence of fundamental photon noise and lateral fiber shifts. We show that both fiber types exhibit comparable noise sensitivity, but GRIN fibers are significantly more robust to lateral misalignment errors. These results establish GRIN MMFs as an alignment-tolerant platform for robust computational microendoscopy.

ALT Pulsed laser sources stand out as remarkable and versatile tools in the growing interdisciplinary field of materials science, offering capabilities for tailoring and customizing materials to meet specific requirements. Their ability to induce different controlled material alterations allows enhancing material properties that might otherwise remain elusive. In essence, laser-induced material modifications encompass a spectrum of transformative processes, ranging from subtle topographical changes in the nano- and microscale, to intricate chemical modifications. Among the challenges to overcome are the creation of approaches that allow tuning the properties of light to optimize interactions on various types of solids, including metals, semiconductors, and dielectrics. Understanding these interactions is paramount towards efficiency increase of the processing techniques. This chapter embarks on a comprehensive exploration of the intricate dance between pulsed laser beams and their interact

ALT Non-Hermitian singularities and the nontrivial topology of energy bands have been extensively explored in extended periodic systems, where phenomena such as exceptional points and bulk Fermi arcs are naturally associated with periodicity and momentum space. Here, we show that this non-Hermitian topology can be extended to the domain of subwavelength resonators using a synthetic space. By reconstructing the complex energy bands of a subwavelength ring resonator in the synthetic space of geometrical parameters, we experimentally observe a spectral triplet formed by two exceptional points (EPs) connected by a bulk Fermi arc and a topologically robust quasi-bound state in the continuum (q-BIC). This Fermi-arc q-BIC emerges exactly at the intersection of the bulk Fermi arc and the q-BIC line in synthetic space, establishing a direct topological link between two spectral singularities. Encircling the EPs in synthetic space visualizes the nontrivial topology of the complex energy-band structu

ALT Lithium Tantalate (LTA) is an important ferroelectric crystal widely used in piezoelectric, electro-optic, and nonlinear optical devices. Although this crystal is very common, there is an ongoing debate regarding its birefringence magnitude, and even its sign. While some sources claim it to be negative, others maintain that it is positive. The issue is further complicated by the sample-to-sample variation in the crystal composition, ranging from congruent to stoichiometric. Here we report the experimental exploration of this question based on high-resolution spectroscopy of optical whispering gallery resonators fabricated from this crystal. These sensitive measurements unambiguously indicate that in the near-infrared range at room temperature the stoichiometric LTA is negative, while the congruent LTA is positive.

ALT We report on a conceptual framework for optical imaging utilizing exclusively evanescent fields, effectively eliminating or attenuating standard optical diffraction. We present the theoretical foundation of this concept based on the decomposition of dipole radiation into evanescent fields and homogeneous propagating waves, exploring the explicit conditions required to suppress the latter. By successfully decoupling and removing the homogeneous component, optical tasks, such as sub-diffraction imaging, can be executed solely via evanescent channels, bypassing traditional diffractive limits. We discuss the physical feasibility of this approach and provide concrete examples of how this conjecture can be realized using currently available laboratory and industrial techniques. The realization of this concept promises to redefine core paradigms in optics and fundamental physics. Because the minimum achievable feature size is no longer governed by the operating wavelength, this approach enabl

ALT Conventional descriptions of light in materials rely on macroscopic models that average the optical response over the microscopic lattice structures. These models are deployed in the semi-classical limit, where the collective local response over many lattice sites is adequate. However, they fail to capture the full spatial dispersion, which requires a lattice-resolved description of light. We address this limitation by formulating a deep-microscopic nonlocal theory of the photon based on the Maxwell Hamiltonian and its characteristic equation. The solution reveals the full spatial dispersion in the form of deep-microscopic photonic bandstructure, and corresponding real-space Bloch field textures. We demonstrate our theory for a two-dimensional (2D) tight-binding model of a gapped honeycomb lattice. Our framework thus extends photons to the same microscopic footing as electrons or phonons, providing a unified route to studying topology, dissipation, and quantum fluctuations of light in

ALT Transparent wood (TW) composites possess residual haze that limits image clarity despite their high light transmission, yet the physical origin of this scattering has not been established. Here, polarization-resolved measurements reveal a pronounced polarization dependence of scattering by a wood-polymer composite with improved refractive index matching. Polarization- and spectrally-resolved haze as low as 21% (40-45% at 550 nm for unpolarized light) with transmittance of approximately 92% for polarization perpendicular to the fibers was detected. It is found that the low-haze spectrum closely follows an inverse-square relation over the 400-800 nm range, well described by a weak-index-contrast Rayleigh-Gans-Debye (RGD) model invoking subwavelength birefringent heterogeneities within the cell wall. This physical mechanism was previously obscured by haze-limiting strong scattering from debonding gaps or refraction at the lumen-cell wall interface. Scanning electron diffraction independen

ALT We investigate whether acoustic stimulation combined with phase-locked optical diffraction tomography (ODT) could measure the mechanical responses of the nucleus and cytoplasm separately in adherent cells. A megahertz ultrasound carrier is amplitude-modulated at low frequencies, while angle-scanned holography provides a route to reconstruct the first-harmonic refractive-index response in three dimensions. We built a computational model connecting viscoelastic finite-element simulations of MDA-MB-231 cells with a refractive-index phantom, hologram formation, camera noise and ODT reconstruction. Under an assumed 0.1 Pa harmonic shear traction at 10 Hz, the model predicts 3.6 to 9.2 nm of nuclear shear and 6.6 to 15.1 nm of apical motion. The nuclear-to-cytoplasmic amplitude ratio (R_A) is primarily sensitive to stiffness contrast in the tested scenarios, while the relative phase (Delta phi) responds to differences in dissipation. A simulated protocol using 100 illumination angles and 16

ALT Double imaging is a common artefact in off-axis single-mirror Schlieren systems. Depending on the distance between the object of interest and the mirror, together with the off-axis imaging geometry, such systems often capture images containing a superposition of the target image and a displaced ghost image, resulting in the so-called double imaging phenomenon. This not only degrades image quality, but also complicates its interpretation. To address this problem, we present a new model for ghost image displacement that takes into consideration finite-aperture support, defocus, and magnification. We then use this model to reconstruct the target image via total variation regularisation with a matrix-free alternating direction method of multipliers (ADMM) algorithm. Extensive experiments using both synthetic and real Schlieren images validate the proposed model, show the effectiveness and efficiency of our algorithm, and evaluate its performance under parameter mismatch. The proposed frame

ALT The spectral characteristics of ultrashort laser pulses offer unique possibilities to control interactions in space and time as well as the subsequent material responses. In particular, selecting the wavelength predefines the fundamental mechanisms governing laser-matter interaction, and thus, how energy is deposited. This Chapter provides an overview on how the essential physical effects in ultrafast laser-matter interaction scale with the wavelength, and the consequences for bandgap material processing applications. First, we recall the main spectral properties of bandgap materials and discuss the important question of the expected processing resolutions depending on wavelength. Then, recent studies on the impact of the wavelength in ultrafast laser-dielectric interaction are presented. Finally, we present how the latest developments in infrared ultrafast laser sources can be advantageously utilized to internally process narrow-gap materials despite challenges related to increased no

ALT Counting the emitters within a diffraction-limited region is a prerequisite for localizing overlapping molecules. Under pulsed excitation, each molecule emits at most one photon per pulse, so photon-number-resolved detection can count emitters without resolving them. But the required number of pulses grows steeply with the emitter number. Here we show that polarization, conventionally used to measure the orientations of dipole emitters, also carries information on their number. Because mean polarization-resolved signals are unchanged when every emitter is replaced by multiple dimmer copies, this information resides in the photon statistics within each pulse, which polarization reshapes in two ways. Linearly polarized excitation at three angles increases the sub-Poissonian deficit of the photon count by a factor of 1.5 for any emitter orientation, and detection in four polarization channels reveals the emitter number through how the photons of multiphoton pulses are distributed among th

ALT Quantitative phase imaging (QPI) has become a standard approach for label-free microscopy of transparent specimens, mapping the optical path length. However, the isotropic phase is blind to the molecular order underlying optical anisotropy. Implementations that also add quantitative contrast to birefringence, rely on multi-frame illumination or polarization-state scanning, or on dedicated interferometric hardware, that trade away acquisition speed or the simplicity of a standard microscope. We present Quantitative Phase and Polarimetric Imaging (QP2I), a computational imaging framework that converts a standard differential interference contrast (DIC) microscope with a polarization camera into a single-shot, video-rate, dual-contrast imaging system. We developed a new globally regularized phase reconstruction that eliminates artifacts of prior DIC-to-QPI approaches, providing quantitative phase information and used per-pixel Stokes-based reconstruction to obtain quantitative anisotropic

ALT Next-generation on-chip photonic devices require compact, energy-efficient components integrating photodetection and light emission on silicon platforms. Achieving broadband photodetection combined with efficient emission in a single nanoscale device remains challenging. Here, we demonstrate elliptical nanopillar arrays monolithically integrated as III-V-on-Si templates, exhibiting broadband photoresponse across visible to near-infrared wavelengths, dynamic neuron-like graded responses under modulated light, and pronounced electroluminescence at around 865 nm under forward bias. The nanostructured elliptical geometry approach enhances optical absorption and carrier dynamics within an active area significantly smaller than commercial detectors, enabling responsivities up to 0.55 A/W at 830 nm in compact nanoarrays. This work advances the development of miniaturized active nanophotonic devices suitable for integrated sensing, emitting and communication circuits, and neuromorphic processi

ALT Chemical characterization of microscopic samples often requires resolving multiple, widely separated vibrational absorption bands, including their positions and spectral shapes. Photothermal microspectroscopy provides a route to localized vibrational measurements by detecting absorption-induced thermal responses with a separate optical probe. However, rapid acquisition of broadband photothermal spectra remains challenging when spectral information is collected through sequential wavelength tuning. Here, we develop a supercontinuum (SC)-driven Fourier-transform photothermal (FT-PT) microspectroscopy platform that combines broadband near-infrared excitation with rapid-scan interferometric acquisition for localized vibrational measurements. In this approach, an interferometrically modulated SC pump induces wavelength-dependent photothermal responses in the sample, which are detected through a co-propagating visible probe beam and reconstructed by Fourier transformation. Using a 1.65-2.35

ALT Cameras in the surf zone or behind ship wakes look through turbid, bubbly, moving water close to the lens, yet restoration networks are usually scored only on displayed images. We introduce a measured dataset of a telescope viewing displayed images and physical objects through a 25 mm water layer 45 mm in front of its objective, under seven combinations of flow, bubbles and turbidity, with clear-water recordings as a second reference. Because the suspension scatters light far outside the 1.3textdegree field of view, turbidity mainly removes contrast, 4.4- to 4.8-fold on a Siemens star. Restoring the mean of eight frames improves structural similarity (SSIM) by 0.032 over a single frame, and learned fusion of the frames adds little. One raw frame supports five-category recognition (96.8\%) as well as restored images. Adding synthetic training pairs leaves display-image scores unchanged but raises the correlation of a restored Siemens star with its clear-water recording from below 0.5 to

ALT This paper develops a stochastic model for quantifying the impact of laser phase noise on photonics-assisted radio frequency (RF) beamforming. Unlike conventional deterministic models, the presented theoretical framework captures the statistical randomness associated with the RF array factor of beamforming networks driven by finite-linewidth lasers. Fourier-domain analysis reveals that laser phase noise reshapes the spatial coherence function of such beamforming networks, inducing coherent RF aperture shrinkage, beam-pattern distortion, and directivity degradation. The analysis highlights that beamforming network architectures employing nanosecond-scale optical differential delays can exhibit substantial performance degradation even when driven by commercially available narrow-linewidth (kHz-range) lasers. Furthermore, it is demonstrated that average RF power gain gets downscaled and fluctuations dominate in large-aperture beamforming networks due to phase noise, imposing an upper limi

ALT The confinement of light within optically thin media challenges the conventional view that optical localization requires high-index dielectric materials and total internal reflection. Over the past decades, a broad range of photonic phenomena has demonstrated that electromagnetic energy can also be guided and localized inside low-index regions or nanoscale void cavities. What first appears to be a curiosity is, in fact, highly relevant: The interaction between light and matter lies at the heart of much in optics and photonics. It enables sensing, nonlinear optical phenomena, and optical manipulation, yet it also inevitably introduces absorption, dissipation, and loss. Pushing localized, enhanced, or guided energy into a lower-index space thus offers entirely new possibilities for light-matter interaction and dispersion control. In this review, we discuss some of these counterintuitive structures, starting with light guidance within optically thin media, such as hollow-core photonic cry

ALT Accurate optical characterization of high-albedo scattering media is fundamentally limited by integrating-sphere measurement errors. Scattering events spatially redistribute photons, leading to lateral beam spread and angular divergence that bias measured reflectance and transmittance. Here, we investigate these deviations, which are quantified and interpreted by using the point spread function (PSF), guided by the radiative transfer equation. Experiments and Monte Carlo modelling show that the widely used external-mount integrating-sphere configuration introduces systematic, configuration-dependent errors that become pronounced when scattering-induced lateral spreading is substantial. Using a normalised PSF to quantify photon redistribution, we map the characteristic lateral spreading length across a broad (τs,g) parameter space in the high-albedo limit, providing a basis for evaluating errors in specific measurement geometries. We further quantify the influence of measurement geometr